YaCy (http://yacy.net) is one of those projects I've heard about for a while, but never actually checked it out until recently. Unlike centralized search engines like google, bing, and duckduckgo, YaCy is decentralized, and run entirely by a network of users, giving you lots more options, and a greater chance of privacy.
This guide will show you how to install and use it on GNU/Linux systems. If you're using Windows, there's also a simple installer you can download too.
Full guide: http://n-o-d-e.net/post/150125231981/yacy-the-p2p-search-engine